Industrial Coatings / General Industrial, Marine and Protective Coatings / Feldspar


Feldspar (silicate, chemical formula Na(AlSi3O8), where Na can also be replaced by K) is one of the main constituents of the Earth’s crust. Feldspar can be characterised by:


  • Relatively high Mohs hardness of 6
  • Low electrical conductivity
  • Easy to wet
  • High inertness in various media.


And, depending on the grade:


  • Low content of lamellar mica (Unispar FF)
  • Low fine crystalline silica fraction (no labelling) (Unispar PG (W))
  • Whiteness (Unispar PG W).


Note when using feldspar: depending on the particle size distribution of certain products, they can be labelled STOT RE 2. For more detailed information, visit

Sibelco feldspar quarry in Cine (Turkey)


Basic properties

Property Value Unit
Moisture < 0.5 [%]
Hardness (Mohs) 6 (6.5) [-]
Refractive index 1.53 [-]
L.O.I. 0.5 [%]
Density 2.6 [kg/ dm3]



Product overview

Product Grade D50





[g/ 100 g]

pH L*
Unispar FF-20 6 n.d. 32 9.8
FF-30 8 n.d. 28 9.7
FF-60 19 n.d. 27 9.5
FF-150 23 n.d. 24 9.4
PG4 4 17 26 9.5 94.5
PG W7* 7 25 27 8.0 97.0
PG W13 13 60 22 8.1 96.4
PG W20 20 80 19 8.2 96.2

Production locations Unispar



Feldspar will provide:


  • Abrasion resistance: due to its hardness of 6 on Mohs scale, feldspar will increase the coating’s resistance to wear.
  • Chemical resistance: due to its inert nature, feldspar will provide good chemical resistance compared to conventional fillers.


Advantage over quartz and cristobalite: several feldspar grades are free of labelling, and can therefore can be used as an alternative when fine quartz or cristobalite grades are no longer allowed.


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